This invention relates to a sensor for force/acceleration/magnetism using piezoelectric elements and, more particularly, to a sensor capable of detecting force, acceleration or magnetism every multi-dimensional respective components.
In the automobile industry or machinery industry, etc., there has been an increased demand for sensors capable of precisely detecting physical action such as force, acceleration or magnetism. Particularly, compact sensors capable of detecting these physical actions every two-dimensional or three-dimensional respective components are being required.
As such a compact sensor, in the U.S. patent application Ser. No. 07/984,435 (European Patent Application No. 92914919.3), a novel sensor which has been developed by the same inventor as that of this application is disclosed. This novel sensor is of a structure such that plural detection elements each comprised of a piezoelectric element are prepared and such detection elements are disposed on a flexible substrate, whereby when an external force is applied to a working body attached on the flexible substrate, bending takes place in the flexible substrate. This bending is transmitted to the piezoelectric element. In the piezoelectric element, charges corresponding to the bending are produced. It is thus the fundamental principle of this sensor that there is employed a method of detecting an applied external force on the basis of the charges produced. Since the manner of how bending takes place varies in dependency upon the direction of an applied external force, the state where charges are produced with respect to a plurality of piezoelectric elements arranged at respective predetermined positions is detected, thereby making it possible to detect the magnitude and the direction of the applied external force.
In the above-described sensor using piezoelectric element, four detection elements are required for the purpose of detecting a force applied in one axial direction. Accordingly, at least eight detection elements are required for the two-dimensional force sensor, and at least twelve detection elements are required for the three-dimensional force sensor. Accordingly, there is the problem that the structure becomes complicated since a large number of detection elements should be arranged on a single flexible substrate. In addition, each detection element has two electrodes of an upper electrode and an lower electrode. Therefore, if independent wirings are respectively implemented to these respective electrodes, the wiring pattern also becomes very complicated.